In reply to thompsongirl:
IMHO they stretch just where you want them to... So the rand doesn't get any longer, but where at first they might feel they're pinching your feet and your toe-knuckles feel crushed, they stretch just enough so your knuckles feel secure but not tight, and your foot feels hugged but not loose.
I drop 2 sizes - they go from "need to release the velcro and get the heel out" between boulder problems to "can wear them on-and-off for a 2-hour session" without pain.
I only stopped buying them as they tend to go through on the toe quite quickly and aren't that cheap to replace. Most of mine got resoled at least once.